CN113524608A - Mold protection method based on extended Kalman filtering - Google Patents

Mold protection method based on extended Kalman filtering Download PDF

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CN113524608A
CN113524608A CN202110777123.6A CN202110777123A CN113524608A CN 113524608 A CN113524608 A CN 113524608A CN 202110777123 A CN202110777123 A CN 202110777123A CN 113524608 A CN113524608 A CN 113524608A
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module
mold
mathematical model
extended kalman
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杨洋
帅炳印
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B29C45/17—Component parts, details or accessories; Auxiliary operations
    • B29C45/84—Safety devices
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
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    • G06F17/00—Digital computing or data processing equipment or methods, specially adapted for specific functions
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    • G06F17/11—Complex mathematical operations for solving equations, e.g. nonlinear equations, general mathematical optimization problems
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    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F30/00—Computer-aided design [CAD]
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    • G06F30/17—Mechanical parametric or variational design

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Abstract

The invention discloses a mold protection method based on extended Kalman filtering, which comprises the following steps: the system comprises a shaft lever mechanism mathematical model module, a servo motor mathematical model module, an extended Kalman filtering module, a self-adaptive module and an execution module. Establishing an ideal current curve for die assembly through a shaft lever mechanism mathematical model module and a servo motor mathematical model module; optimizing a measured actual curve according to the ideal current curve through the established extended Kalman filtering module; the adaptive module opens and closes the mold for multiple times to form an optimized curve group, and the upper limit and the lower limit are calculated to form a protection interval; and the execution module monitors whether the current exceeds the interval during actual operation, and opens the die and gives an alarm if the current exceeds the interval. According to the method, when foreign matters appear in the mold closing process of the injection molding machine, the mold closing is stopped to protect the mold from being damaged, and compared with the traditional method, the precision of mold protection is improved through the optimization of an actual curve.

Description

Mold protection method based on extended Kalman filtering
Technical Field
The invention belongs to the field of plastic injection molding, and relates to a mold protection method based on extended Kalman filtering.
Background
Plastic articles are seen everywhere, most of the products are injection molded. Injection molding machines are being developed toward high speed, high precision, low power consumption, and low noise. Electric injection molding machines with toggle-link mechanisms driven by permanent magnet synchronous motors are typical of the process development. In injection molding, the problem of protecting the mold under high-speed and high-precision control becomes more and more severe because the mold is expensive, various and troublesome to maintain. At present, two methods are mainly used, one method is used for detecting foreign matters through comparison before and after image processing based on vision, and an additional vision system is required to be installed; in the other type, whether the mold needs to be protected or not is judged by manually setting a current threshold value during mold closing, but the manual setting parameters are not easy to determine and the precision is low.
Disclosure of Invention
Therefore, the invention provides a mold protection method based on extended Kalman filtering. The method comprises but is not limited to a shaft rod mechanism mathematical model module, a servo motor mathematical model module, an extended Kalman filtering module, an adaptive module and an execution module basic unit. The method can optimize the measured current value according to a theoretical current curve and adaptively establish a protection interval for mold protection, thereby improving the mold protection precision, and comprises the following steps:
s1, establishing an ideal current curve for die assembly through a shaft lever mechanism mathematical model module and a servo motor mathematical model module;
s2, optimizing the actual curve obtained by measurement according to the ideal current curve through the established extended Kalman filtering module;
s3, opening and closing the mold by the self-adaptive module for multiple times to form an optimized curve group, and calculating the upper limit and the lower limit to form a protection interval;
and S4, the execution module monitors whether the current exceeds the interval during actual operation, and if the current exceeds the interval, the execution module opens the die and gives an alarm.
Preferably, the ideal curve calculation means that the ideal curve is obtained by converting a set track curve through a shaft mechanism mathematical model and a servo motor mathematical model.
Preferably, the adaptive module needs to obtain a protection interval before the execution module executes.
Preferably, the protection interval refers to the upper and lower current limits according to each position in the mold closing process of the injection molding machine.
Preferably, the electric injection molding machine is characterized by comprising but not limited to an injection part, a mold closing part, a base and a mold. The servo motor system drives a screw rod in the injection part to inject molten plastic into a mold for molding to obtain a plastic product.
The negative side beneficial effects at least comprise: the method optimizes a measured current curve, and adaptively obtains a protection interval to realize the protection of the mold. The invention realizes the high-quality and consistent production of plastic products through the feedback and the predictive control of the specific volume.
Drawings
FIG. 1 is an application object of a mold protection method based on extended Kalman filtering according to an embodiment of the present invention;
FIG. 2 is a step executed by the mold protection method based on extended Kalman filtering according to the embodiment of the present invention;
FIG. 3 is a flowchart of a mold protection method based on extended Kalman filtering according to an embodiment of the present invention;
FIG. 4 is a shaft mechanism in the extended Kalman filter based mold protection method according to the embodiment of the present invention;
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
On the contrary, the invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, certain specific details are set forth in order to provide a better understanding of the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details.
The invention relates to a mold protection method based on Kalman filtering, which comprises but is not limited to a shaft rod mechanism mathematical model module, a servo motor mathematical model module, an extended Kalman filtering module, an adaptive module and an execution module basic unit. The application object of the method is shown in figure 1. The execution steps are as shown in fig. 2, and are explained as follows:
s1, establishing an ideal current curve for die assembly through a shaft lever mechanism mathematical model module and a servo motor mathematical model module;
s2, optimizing the actual curve obtained by measurement according to the ideal current curve through the established extended Kalman filtering module;
s3, opening and closing the mold by the self-adaptive module for multiple times to form an optimized curve group, and calculating the upper limit and the lower limit to form a protection interval;
and S4, the execution module monitors whether the current exceeds the interval during actual operation, and if the current exceeds the interval, the execution module opens the die and gives an alarm.
Specifically, as shown in fig. 3, it includes a training portion and an application portion.
The training part calculates an ideal current curve through the established shaft lever mechanism mathematical model and the servo motor mathematical model according to the set track curve. And the established extended Kalman filtering model filters and measures a current curve according to the ideal current curve. And establishing a current protection interval through the self-adaptive module.
And in the application part, in the process of producing products by the electric injection molding machine, if the actual current is not in the current protection interval, starting a protection program, and immediately opening the mold. Particularly, if the current is in the protection interval, the current actual curve and the set curve are fed back to the training part, and the current protection interval is continuously optimized.
The construction process of the toggle mechanism mathematical model is as follows:
the toggle mechanism is shown in fig. 4, and a cartesian coordinate system is established with a pivot point 1 in the figure as an origin for constructing kinematic and kinetic equations. In the figure, FC，FBIs the force acting on the sliders C and B; m is2，m3，m5，mb，mcThe weight of the toggle levers 2, 3, 5 and the slider B, C; r is1，r2，r4The length of each side of the rod 2; r is3，r5Is the length of the rods 3, 5; f is the distance from the sliding block B to the x axis; h is the height between the sliders B and C. From the toggle lever mechanism characteristics, a constraint equation can be derived：
Figure BDA0003155976780000031
Can be calculated according to the characteristics of (5) and figure [1]
Figure BDA0003155976780000032
According to Hamilton principle, there are
Figure BDA0003155976780000033
T1Is the kinetic energy of the system, δ WAIs deficiency work, QCIs the system constraint. Wherein
Figure BDA0003155976780000041
Figure BDA0003155976780000042
Thereby can obtain
Figure BDA0003155976780000043
According to the desired trajectory xBCan be solved to obtain:
Figure BDA0003155976780000044
all data calculation formulas are as follows:
Figure BDA0003155976780000045
Figure BDA0003155976780000046
wherein
Figure BDA0003155976780000047
Figure BDA0003155976780000048
Figure BDA0003155976780000049
Figure BDA00031559767800000410
Figure BDA00031559767800000411
Figure BDA00031559767800000412
Figure BDA00031559767800000413
Figure BDA0003155976780000051
Figure BDA0003155976780000052
Figure BDA0003155976780000053
Figure BDA0003155976780000054
Figure BDA0003155976780000055
Figure BDA0003155976780000056
The calculation formula is as follows:
Figure BDA0003155976780000057
Figure BDA0003155976780000058
Figure BDA0003155976780000059
Figure BDA00031559767800000510
the mathematical model of the servo motor is constructed as follows:
τe＝Kti(t) (5)
wherein i (t) is current, KtIs the stator torque constant. Tau iseThe following can be obtained from the mechanical equation:
Figure BDA00031559767800000511
where l is the ball screw lead, η screw drive efficiency. Thus, the relationship between current and force on the slider C can be obtained as follows:
Figure BDA00031559767800000512
the extended kalman filter model is as follows:
as filtering targets, taking i (t) and h (t) as predicted values and measured values in the extended kalman filtering, obtaining a state transition equation and an observation equation:
Figure BDA00031559767800000513
where r is the process standard deviation and q is the measurement standard deviation. Obtaining a Jacobian matrix:
Figure BDA0003155976780000061
based on the above formula, the covariance update equation is given:
Figure BDA0003155976780000062
wherein Q is the deviation of the process and,
Figure BDA0003155976780000063
is FtThe transposing of (1).
According to the set curve and the feedback current, the current optimal estimation is as follows:
X(t|t)＝X(t|t-1)+Kg(t)(Z(t|t-1)-HtX(t|t-1)), (9)
wherein, Kg(t) is the Kalman gain, which can be obtained by the following equation:
Figure BDA0003155976780000064
where R is the measurement deviation.
To keep the extended kalman filter running continuously, the covariance update equation is as follows:
P(t|t)＝(I-Kg(t)Ht)P(t|t-1), (11)
where I is the identity matrix.
The adaptive module is constructed as follows:
and under the condition of ensuring that no foreign matter exists in the die, performing adaptive module execution, wherein the adaptive frequency is n. The current curve executed each time is stored to the matrix A according to the dimension of the position vector Pm×nExpressed as follows:
Figure BDA0003155976780000065
the upper and lower limits U, L of the guard interval are calculated as follows:
Figure BDA0003155976780000066
wherein Δ is calculated by the following method:
Figure BDA0003155976780000067
wherein
Figure BDA0003155976780000068
Is the arithmetic mean of the n-th order.

Claims (5)

1. A mold protection method based on extended Kalman filtering is characterized by comprising but not limited to a shaft rod mechanism mathematical model module, a servo motor mathematical model module, an extended Kalman filtering module, an adaptive module and an execution module basic unit. Inter-unit execution, comprising the steps of:
s1, establishing an ideal current curve for die assembly through a shaft lever mechanism mathematical model module and a servo motor mathematical model module;
s2, optimizing the actual curve obtained by measurement according to the ideal current curve through the established extended Kalman filtering module;
s3, opening and closing the mold by the self-adaptive module for multiple times to form an optimized curve group, and calculating the upper limit and the lower limit to form a protection interval;
and S4, the execution module monitors whether the current exceeds the interval during actual operation, and if the current exceeds the interval, the execution module opens the die and gives an alarm.
2. The extended kalman filter-based mold protection method according to claim 1, wherein the ideal current curve is obtained by converting a shaft mechanism mathematical model and a servo motor mathematical model according to a set trajectory curve.
3. The extended kalman filter-based mold protection method according to claim 1, wherein the adaptive module needs to obtain a protection interval before the execution module executes.
4. The mold protection method based on the extended kalman filter according to claim 3, wherein the protection interval refers to an upper current limit and a lower current limit according to each position in a mold closing process of the electric injection molding machine.
5. An electric injection molding machine, which is characterized by comprising but not limited to an injection part, a mold closing part, a base, a mold and a servo motor system. The servo motor system drives a screw rod in the injection part to inject molten plastic into a mold for molding to obtain a plastic product.
CN202110777123.6A 2021-07-09 2021-07-09 Mold protection method based on extended Kalman filtering Pending CN113524608A (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01215525A (en) * 1988-02-25 1989-08-29 Idemitsu Petrochem Co Ltd Control method for injection compression molding machine
CN103718118A (en) * 2011-08-30 2014-04-09 川崎重工业株式会社 Adaptive control device and adaptive control method, as well as control device and control method for injection molding machine
KR101582675B1 (en) * 2014-06-27 2016-01-05 남부대학교산학협력단 temperature control apparatus of heating and cooling mold using extended kalman filter
CN107065551A (en) * 2017-04-24 2017-08-18 哈尔滨工大航博科技有限公司 A kind of artificial rotary table automatic correction controling method accurately recognized based on model parameter
CN108312455A (en) * 2017-12-07 2018-07-24 海天塑机集团有限公司 A kind of method of controlling security and system of electric injection molding machine crank type clasp mould mechanism

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01215525A (en) * 1988-02-25 1989-08-29 Idemitsu Petrochem Co Ltd Control method for injection compression molding machine
CN103718118A (en) * 2011-08-30 2014-04-09 川崎重工业株式会社 Adaptive control device and adaptive control method, as well as control device and control method for injection molding machine
KR101582675B1 (en) * 2014-06-27 2016-01-05 남부대학교산학협력단 temperature control apparatus of heating and cooling mold using extended kalman filter
CN107065551A (en) * 2017-04-24 2017-08-18 哈尔滨工大航博科技有限公司 A kind of artificial rotary table automatic correction controling method accurately recognized based on model parameter
CN108312455A (en) * 2017-12-07 2018-07-24 海天塑机集团有限公司 A kind of method of controlling security and system of electric injection molding machine crank type clasp mould mechanism

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
CHEN BAIPING, WU HUIFENG, ZHOU HONGWEI, SUN DANFENG *

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